It has long been known from thermodynamics and the literature that, in principle, useful energy can be made available when dilute and concentrated solutions are mixed. As known in the art, a naturally occurring, diffusion-driven, spontaneous transport of ions occurs throughout a solution matrix, thru barrier interfaces, or thru ion-selective membranes from the side containing the salts of higher concentration to the compartments containing the more dilute solution to effect the equalization of concentration of the ionic species. Since this ion movement consists, preferentially, of either cations or anions, it leads to a charge separation, otherwise known as a potential difference across the membrane. Eventually, the membrane gradually opposes further charge transfer buildup and thus equilibrium is established at a specific value of the potential difference.
In previous disclosures, pathways are separated by a cation/anion membrane stack, such as those found in Electrodialysis (ED) units where direct current provides the motive force for ion migration from the low concentration side to the higher concentration side. Because concentration gradient driven systems force ion migration from the high concentration side to the low, these systems are sometimes referred to as Reverse Electrodialysis or Dialytic systems (not to be confused with Electrodialysis Reversal (EDR) systems in which the polarity of the ED electrodes are periodically reversed to aid in the breaking up and flushing out of scales, slimes and other deposits from the membrane stack).
One such dialytic system as disclosed in the art describes a series of 40 pairs of cation and anion-exchange membranes that form a stack to generate electricity in a dialytic flow battery structure. Here, two saline solutions of differing concentrations were allowed to flow along the sides of the membranes to affect the potential difference. Because of the use of a two-membrane system, the resultant flow structure becomes complicated, especially when a plurality of cells are used in tandem. An additional system known in the art, utilizes river and seawater thus establishing the difference in salinity and ion concentrations. No mention is made of the number of cells needed to produce electricity, and it is again noted that separate anion and cation membranes are used. In another system known in the art, a river and seawater dialytic battery is disclosed. Again the compartments are stacked and range from 10 to 40 pairs of anion/cation membranes. Again, a dual membrane system is employed is this system as disclosed.
It is evident from the prior art that there is a need for a simplified electric current generating system that does not suffer from the complexities of the dual membrane systems known in the art and which is also capable of generating useful electric current which can be used to power systems both integral to the battery or fuel cell or isolated therefrom.